Tanks for holding an operating medium are known for holding operating substances such as oil or fuel which function to supply a work tool with oil or to supply fuel to an engine. A tank for an operating medium for an internal combustion engine of a portable handheld work apparatus is blown as one piece from plastic and has a fill opening and an output opening for the operating medium. The operating medium tank is provided with assembly openings for mounting on the drive unit. Attachment elements for connecting the tank to the drive unit are guided through the assembly openings. In an operating medium tank, the assembly on the drive unit is made difficult especially because of a lack of adjusting devices. In addition, the danger is present that the operating medium tank will develop a leak because of possible fractures of the assembly openings.